Liquid crystal display device

ABSTRACT

In a liquid crystal display device of the present invention, a recessed portion is formed in a portion of a periphery of a lower frame, a columnar member is provided to the recessed portion, the columnar member is allowed to pass through a hole formed in a projecting portion which is provided to an optical sheet, and a side surface of a liquid crystal panel is brought into contact with the columnar member. The columnar member provided to the lower frame not only determines the position of the liquid crystal panel with respect to the lower frame but also determines the position of the optical sheet with respect to the lower frame and firmly holds the optical sheet to the lower frame thus preventing the disengagement of the optical sheet from the lower frame.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a liquid crystal display device,and more particularly, to a liquid crystal display device which canenhance the reliability thereof by holding an optical sheet interposedbetween a liquid crystal panel and a backlight which is arranged at aback surface of the liquid crystal panel and the liquid crystal panel ata given position and preventing the positional displacement from eachother.

[0003] 2. Description of the Related Art

[0004] A liquid crystal display device which is capable of performing acolor display of high definition for a notebook type computer or acomputer monitor is provided with a light source for illuminating aliquid crystal panel from a back of the panel (a so-called backlight)and an optical sheet which is interposed between the backlight and theliquid crystal panel for correcting light from the backlight to a givenbrightness distribution with respect to the liquid crystal panel.

[0005] The liquid crystal panel which constitutes this type of liquidcrystal display device basically sandwiches a liquid crystal layerbetween two substrates at least one of which is formed of a transparentsubstrate such as a glass plate or the like. This type of liquid crystalpanel is roughly classified into a type which turns on and off givenpixels by selectively applying voltages to various kinds of electrodesfor forming pixels which are formed on the substrate (simple matrix) anda type which forms the above-mentioned various kinds of electrodes andactive elements for selecting pixels and turns on and off given pixelsby selecting the active elements (active matrix). Currently, focusing ona fact that the active matrix type liquid crystal panel hascharacteristics such as high definition and high-speed display, theactive matrix liquid crystal panel has been popularly used.

[0006] The conventional active matrix type liquid crystal display deviceadopts a so-called vertical electric field type in which an electricfield is applied between pixel electrodes which are formed on onesubstrate and a common electrode which is formed on the other substrateso as to change the orientation direction of the liquid crystal layer(see Japanese Laid-open Patent Publication 309921/1988).

[0007] On the other hand, there has been realized a so-called liquidcrystal display device of a lateral electric field type (also referredto as “IPS type”) which makes the direction of the electric fieldapplied to the liquid crystal layer substantially parallel to a surfaceof the substrate. As the liquid crystal display device of this lateralelectric field type, there has been proposed a display device which canobtain an extremely wide viewing angle using comb electrodes at one oftwo substrates (see Japanese Laid-open Patent Publication 21907/1988,U.S. Pat. No. 4,345,249).

[0008] In any one of the above-mentioned liquid crystal display devices,as an illumination light source of the liquid crystal panel, there havebeen known a side edge backlight which is constituted of a light guideplate and a linear lamp and a direct backlight which directly installs aplurality of linear light sources at a back surface of the liquidcrystal panel.

[0009] Particularly, the side edge backlight is constructed as follows.The linear lamp (cold cathode fluorescent lamp, for example) is arrangedalong at least one side edge of the light guide plate which isconstituted of a transparent plate such as an acrylic plate. Lightirradiated from the linear lamp is introduced into the light guide plateand a path of the light is changed in the course of propagation in theinside of the light guide plate and is irradiated from the light guideplate. Then, the light is corrected to a given brightness distributionby means of an optical sheet which has a laminated structure made of alight diffusion sheet and a prism and then the light illuminates theliquid crystal panel disposed above the optical sheet.

[0010] The liquid crystal display device is assembled into a so-calledliquid crystal display module by integrating the liquid crystal paneland the backlight together with the optical sheet using an upper frameand a mold case (also referred to as “lower frame”). Usually, the lightguide plate which constitutes the backlight is fitted into the mold casewhich constitutes the lower frame and, thereafter, the optical sheet ispositioned on the mold case. Then, the liquid crystal panel is mountedon and is positioned on the optical sheet.

[0011] However, the optical diffusion sheet and the prism sheet whichconstitute the optical sheet are extremely thin film-like members. Thesefilm-like members must be positioned at a given position on the lowerframe. Further, it is necessary to prevent the positional displacementand the disengagement of the film-like members in the course ofconveying in a manufacturing process or in the course of transporting toan assembly plant.

[0012]FIG. 17A and FIG. 17B are schematic views for explaining aconventional example of a structure for positioning and holding anoptical sheet in a liquid crystal display device, wherein FIG. 17A is across-sectional view of an essential part and FIG. 17B is a developedperspective view of the essential part.

[0013] In FIG. 17A and FIG. 17B, MCA indicates a lower frame which isformed by a resin mold and is configured to house a reflection sheetRFS, a light guide plate GLB, an optical sheet OPS, a liquid crystalpanel and the like. The reflection sheet RFS is mounted on the lowerframe MCA and the light guide plate GLB fitted into the reflection sheetRFS from above. The optical sheet OPS is positioned on the light guideplate GLB.

[0014] In this example, as shown in FIG. 17B, the optical sheet OPS isconstituted of four film members in total, wherein optical diffusionsheets SPS are laminated to both sides of two prism sheets PRS whosegroove directions cross each other. A projecting portion (lug) TAB isformed on one of peripheries of the optical sheet OPS and the opticalsheet OPS is positioned by allowing a columnar member (pin) PIN which ismounted on the lower frame MCA to pass through a hole HOL formed in theprojecting portion TAB. Thereafter, a cylindrical sleeve SB made ofsilicone or rubber is fitted on the columnar member PIN from above thecolumnar member PIN so as to fix the optical sheet thus preventing theremoval or the disengagement of the optical sheet OPS from the columnarmember PIN.

[0015] Then, the liquid crystal panel PNL is assembled into the lowerframe MCA and then is covered with an upper frame SHD. Subsequently, theupper frame SHD is fixed to the lower frame MCA so as to form anintegrated liquid crystal display module.

[0016] The mounting position of the columnar member PIN is usuallydisposed at one of peripheries of the lower frame MCA so as to avoid aside of the liquid crystal panel PNL on which a driver is mounted and aportion thereof where a liquid crystal filling and sealing opening isformed. A similar structure or a structure which simply holds theoptical sheet loosely is provided at other peripheries of the lowerframe MCA.

[0017]FIG. 18A and FIG. 18B are schematic views for explaining otherconventional example of the positioning of an optical sheet in a liquidcrystal display device and a holding structure thereof, wherein FIG. 18Ais a cross-sectional view of an essential part and FIG. 18B is a planview of the essential part. Numerals which are as same as those of FIG.17A and FIG. 17B indicate identical functional portions.

[0018] In this example, U-shaped walls WL which surround projectingportions TAB formed on an optical sheet OPS from three directions areformed in four peripheries of a lower frame, and the projecting portionsTAB formed on the optical sheet OPS are fitted into and seated inrecessed portions formed in these U-shaped walls WL so as to perform thepositioning of the optical sheet OPS.

[0019] Further, there may be a method in which such U-shaped walls WLare formed only at opposing two peripheries or neighboring peripheriesor the U-shaped wall WL is formed at only one periphery and the opticalsheet OPS and the lower frame are fixed to each other using an adhesivetape or the like at peripheries which are not provided with the U-shapedwalls WL.

[0020]FIG. 19 is a developed perspective view of an essential part forexplaining a further conventional example of positioning of an opticalsheet in a liquid crystal display device and a holding structurethereof. In this conventional example, recessed portions DH are formedin front and back surfaces of a lower frame MCA. Columnar members PINsimilar to the columnar members PIN of the example explained inconjunction with FIG. 17A and FIG. 17B are formed such that they areprojected at both front and back sides of the recessed portions DH. Aprojecting portion TAB which is formed on the optical sheet OPS isseated in the front-side recessed portion DH such that the columnarmember PIN is allowed to pass through a hole HOL formed in theprojecting portion TAB. Thereafter, a clip CLM is fitted on the columnarmembers PIN which are projected at both front and back sides of therecessed portions DH.

[0021] This clip CLM is provided with an opening PR1 into which thefront-side columnar member PIN is fitted from the lateral direction andan opening PR2 into which the back-side columnar member PIN is fittedfrom the lower direction. The clip is formed of a metallic resilientmaterial and resiliently fixes the optical sheet OPS to the lower frameMCA.

[0022] As literatures which disclose the above-mentioned related art,for example, Japanese Laid-open Patent Publication 281966/1999, JapaneseLaid-open Patent publication 90361/1997 and Japanese Laid-open PatentPublication 258756/2000 are named.

SUMMARY OF THE INVENTION

[0023] The structure for positioning the optical sheet to the lowerframe in the above-mentioned conventional liquid crystal display devicehas a following drawbacks to be solved.

[0024] With respect to the conventional structure which has beenexplained in conjunction with FIG. 17A and FIG. 17B, the columnar memberPIN is required to ensure the height for making the sleeve SB fit on thecolumnar member PIN so that a projecting quantity from the lower frameMCA is increased. When this projecting quantity is increased, the sizeof the lower frame in the member thickness direction is increased sothat a special care is required in packaging of parts or the chippingmay occur at the time of transporting or handling the lower frame MCAbefore advancing to an assembling step. Further, in this constitution,the positioning of the liquid crystal panel PNL is irrelevant to thepositioning of the optical sheet OPS.

[0025] With respect to the conventional example which has been explainedin conjunction with FIG. 18A and FIG. 18B, the optical sheet OPS has theprojecting portions TAB thereof simply fitted into the U-shaped walls WLfrom above. Accordingly, at the time of conveying in the manufacturingstep or at the time of transporting to other manufacturing section, theabove-mentioned projecting portions TAB fall from the U-shaped walls WLor the positional displacement of the optical sheet OPS arises. Further,also in this constitution, the positioning of the liquid crystal panelPNL is irrelevant to the positioning of the optical sheet OPS.

[0026] In the conventional structure shown in FIG. 19, since themetallic clip CLM is used for securing the optical sheet OPS, thepossibility that the metallic clip CLM is brought into pressure contactwith a liquid crystal panel laminated above the optical sheet OPS andgives an unexpected damage to the liquid crystal panel can not bedenied. Further, the use of such a metallic clip CLM becomes one ofobstacles which hampers the reduction of cost.

[0027] Further, none of the above-mentioned related arts suggests thepositioning of the liquid crystal panel which is mounted on the opticalsheet after mounting the optical sheet on the lower frame.

[0028] Accordingly, it is an object of the present invention to solvevarious problems of the above-mentioned related arts and to provide aliquid crystal display device which can provide the reliable positioningand the holding of the optical sheet to the lower frame and can use apositioning guide of a liquid crystal panel and positioning means of theoptical sheet in common, whereby the liquid crystal display device canhave a structure capable of suppressing the removal or disengagement ofthe optical sheet assembled to the lower frame at the time oftransporting or at the time of transferring so as to reduce man-hoursfor assembling and simplifying the operation and reducing themanufacturing cost.

[0029] To achieve the above-mentioned object, in the present invention,a recessed portion (an indentation formed in a side wall whichconstitutes a frame, for example) is formed in a frame member (a lowerframe, a mold case, for example) which holds and secures a light guideplate, an optical sheet and a liquid crystal panel, a columnar member ismounted or formed on the recessed portion, an optical sheet having aprojecting portion in which a through hole is formed allows the columnarmember to pass through the through hole, whereby the optical sheet ispositioned and held in the frame member, wherein the columnar memberalso functions as a guide for determining the position of the liquidcrystal display panel with respect to the frame member. To describe thetypical constitutions of the present invention, they are as follows.

[0030] Constitution (1):

[0031] The liquid crystal display device includes a liquid crystal panel(also referred to as “a liquid crystal display panel” or “a liquidcrystal display element”), a backlight which is mounted on a backsurface of the liquid crystal panel through an optical sheet, arectangular lower frame (a mold case) which houses the backlighttherein, and an upper frame (a metal case) which forms a picture framefor exposing an effective display area of the liquid crystal panel, hasside walls extending toward the lower-frame side and is fixed to theupper frame, wherein

[0032] the liquid crystal display device further includes a columnarmember at a portion of a periphery of the lower frame which is servedfor restricting and holding the optical sheet at a given position aswell as for positioning the liquid crystal panel at a given position,and the optical sheet includes a through hole which allows the columnarmember to pass therethrough at a side portion thereof which correspondsto the periphery on which the columnar member is mounted.

[0033] The back surface of the liquid crystal panel means one of a pairof main surfaces of the liquid crystal panel which is positioned at aback of the liquid crystal panel (the liquid crystal display device onwhich the liquid crystal panel is mounted in a strict sense) as viewedfrom a user. Irrespective of the shape, any backlight including a sideedge backlight which arranges a light guide plate at a back surface ofthe liquid crystal panel in an opposed manner and a direct backlightwhich arranges a plurality of light sources at a back surface of theliquid crystal panel in an opposed manner can be used. The effectivedisplay area means an area which is served for reproduction of desiredimages within the main surface of the liquid crystal panel. The throughhole means a so-called opening and the through hole can be formed intoany suitable shape.

[0034] Constitution (2):

[0035] The optical sheet shown in the constitution (1) includes at leastone light diffusion sheet or at least one prism sheet and is constitutedby laminating at least one light diffusion sheet and at least one prismsheet when necessary.

[0036] The liquid crystal display device which performs the activematrix driving in an In-Plane Switching (hereinafter abbreviated as“IPS”) system uses a so-called direct backlight which arranges aplurality of tubular light sources such that these light sources facethe main surface of the liquid crystal panel in an opposed manner andhence, it is preferable to use a diffusion plate as at least one lightdiffusion sheet.

[0037] Further, the liquid crystal display device mounted on a notebooktype computer adopts a so-called side edge backlight which makes a lightguide plate formed of acrylic resin or the like face a main surface of aliquid crystal panel in an opposed manner and arranges at least onetubular light source at a side surface thereof (the tubular light sourcebeing prevented from facing at least an effective display area of themain surface of the liquid crystal panel). However, it may be possibleto use a prism sheet which has a prism surface at the light guide plateside as at least the above-mentioned one prism sheet. Further, it ispreferable to use a light guide plate which has a light scatteringsurface at a prism sheet side thereof.

[0038] In any cases, a projecting portion is formed at a side portion ofthe optical sheet which corresponds to a periphery of the lower frame onwhich the columnar member is mounted and a through hole which allows thecolumnar member to pass therethrough is formed in the projecting portionof the optical sheet.

[0039] Constitution (3):

[0040] In the constitution (2), a recessed portion which accommodatesthe projecting portion of the optical sheet is formed in the peripheryof the lower frame where the columnar member is mounted, and thecolumnar member is allowed to pass through the through hole formed inthe projecting portion of the optical sheet so that the optical sheet isfixed to the lower frame.

[0041] Constitution (4):

[0042] In the constitution (1), the columnar member which is mounted onthe lower frame is allowed to pass through the through hole formed inthe optical sheet and, with the use of an adhesive tape, the opticalsheet is fixed to the periphery of the lower frame where the columnarmember is mounted.

[0043] Constitution (5):

[0044] In the liquid crystal display device defined by the constitutions(1) to (4), another optical sheet holding structure holding the opticalsheet loosely in comparison with the aforementioned structure holdingthe optical sheet by the columnar member and the through hole is newlyprovided to one of peripheries of the lower frame other than theperiphery thereof having the columnar member (also called as “a firstside of the lower frame”). The other periphery of the lower frame is oneof the peripheries thereof arranged adjacent to the aforementionedperiphery thereof having the columnar member (a second side beingtransverse to the first side) or arranged opposite to the aforementionedperiphery thereof having the columnar member (a third side beingopposite to the first side).

[0045] Constitution (6):

[0046] The optical sheet holding structure in the constitutions (1) to(5) is constituted by a columnar projection which is formed on one ofthe above-mentioned neighboring peripheries or the above-mentionedopposite periphery of the lower frame and an opening which is formed onother periphery of the optical sheet and allows the columnar projectionto loosely pass therethrough.

[0047] Constitution (7):

[0048] The optical sheet holding structure in the constitutions (1) to(5) is constituted of a recessed portion which is formed in one of theabove-mentioned neighboring peripheries or the above-mentioned oppositeperiphery of the lower frame and a projecting portion which is formed ona portion of the optical sheet corresponding to the recessed portion andis seated in the recessed portion.

[0049] Constitution (8):

[0050] The optical sheet holding structure in the constitution (7) isprovided with a disengagement restriction member which restricts thedisengagement of the projecting portion of the optical sheet from therecessed portion.

[0051] Constitution (9):

[0052] The columnar member in the constitution (1) or (2) is integrallyformed with the lower frame (mold case).

[0053] Constitution (10):

[0054] The columnar member in the constitution (1) or 1(2) is formedseparately from the mold case and is fitted into the lower frame (moldcase) through a hole formed in the lower frame (mold case).

[0055] Constitution (11):

[0056] The portion of the columnar member in the constitution (9) or(10) for positioning the liquid crystal panel is shaped so that the sizethereof in the direction opposite to the liquid crystal panel isdifferent from the size of a portion for holding the optical sheet beingformed integrally with or separately from the columnar member.

[0057] Due to the above-mentioned respective constitutions, thepositioning and the holding of the optical sheet to the lower frame(mold case) can be reliably performed and, at the same time, thisfunction can be also used as a function of a guide for positioning theliquid crystal panel which is mounted on the optical sheet in asuperposed manner so that the removal or the disengagement of theoptical sheet at the time of conveying or transporting the lower frameinto which the optical sheet is incorporated can be suppressed. Further,since the man-hours for assembling can be reduced, the operation issimplified and the manufacturing cost can be reduced.

[0058] On the other hand, in the liquid crystal display device describedhereinafter, the present invention is embodied in any one of modes offollowing constitutions (12) to (24).

[0059] The liquid crystal display device illustrated here includes aliquid crystal panel, a backlight which is arranged to face a first mainsurface of the liquid crystal panel (a back surface of the liquidcrystal panel as viewed from a user of the liquid crystal displaydevice) in an opposed manner, an optical sheet (see, the above-mentionedconstitution (2) with respect to the constitutional content) which isarranged between the first main surface of the liquid crystal panel andthe backlight, a first frame (lower frame in the above-mentionedconstitution (1)) having a rectangular shape which accommodates thebacklight, and a second frame (an upper frame in the above-mentionedconstitution (1)) which is formed in a picture frame and covers at leasta portion of a periphery of a second main surface (a user-side surfaceof the liquid crystal display device, a so-called front surface of theliquid crystal panel) which faces the first main surface of the liquidcrystal panel in an opposed manner and a side surface formed on thefirst frame.

[0060] In the liquid crystal panel, a liquid crystal layer is sandwichedby a pair of substrates (transparent substrates having insulation) andelectrodes and wiring patterns which apply an electric field to theliquid crystal layer are formed on a liquid-crystal-layer side mainsurface of at least one of these substrates.

[0061] The backlight includes not only a substantial light source suchas a cold cathode fluorescent lamp or a light emitting element but alsoa backlight system, a backlight unit or an illumination device which isprovided with optical elements which are disposed between the lightsource and the liquid crystal element.

[0062] With respect to the direct backlight which arranges a pluralityof tubular light sources such that the tubular light sources face thefirst main surface of the liquid crystal panel in an opposed manner, areflection plate which is arranged at a side opposite to the opticalsheet (arranged between the tubular light sources and the first mainsurface of the liquid crystal panel) with respect to the tubular lightsource may be included in the backlight. On the other hand, with respectto a side edge backlight which arranges a light guide plate (an opticalelement made of acrylic resin or the like) such that a main surface ofthe light guide plate faces the first main surface of the liquid crystalpanel, at least one tubular light source is arranged to face a sidesurface of the light guide plate and a reflection sheet is arranged onother main surface of the light guide plate, these light guide plate andthe reflection sheet may be included in the backlight.

[0063] A so-called mold case which is formed by molding synthetic resin,for example, is used as the first frame. In the liquid crystal displaydevice of this example, on one of the main surfaces (including openingsformed therein) of the first frame (referred to as “a bottom surface ofthe first frame” hereinafter), the backlight, the optical sheet and theliquid crystal panel are laminated in this order, and the periphery ofthe second main surface of the liquid crystal panel is suppressed by aso-called picture frame of the second frame thus assembling the liquidcrystal display device.

[0064] As the second frame, a shield case which is produced by forming awindow (exposing the effective display area of the liquid crystal panel)in a bottom surface of a metal frame which is formed in a frame using ametal plate, or a metal case which is formed in a box shape can be usedfor example.

[0065] To apply the present invention to the liquid crystal displaydevice of the example explained above, such a liquid crystal displaydevice exhibits following constitutional features.

[0066] Constitution (12):

[0067] When the periphery of the bottom surface of the first frame isconstituted by including a first pair of sides which face each other inan opposed manner and a second pair of sides which extend in thedirection intersecting a first pair of sides and face each other in anopposed manner, at least one first columnar member is mounted on one(first periphery) of a first pair of sides of the main surface of thefirst frame which faces the second frame, at least one second columnarmember is mounted on one (second periphery) of a second pair of sides ofthe main surface of the first frame which faces the second frame in anopposed manner, a first opening into which the first columnar member isfitted is formed in a periphery (first periphery) of the optical sheetwhich faces one of a first pair of sides of the first frame, and asecond opening into which the second columnar member is fitted is formedin a periphery (second periphery) of the optical sheet which faces oneof a second pair of sides.

[0068] Assuming that the first frame has a rectangular bottom surface,the bottom surface of the first frame and the first periphery and thesecond periphery of the optical sheet are extended in an L-shape fromone corner of the bottom surface. That is, the positional displacementof the optical sheet with respect to the first frame is prevented by twosides of the first frame which are extended in the L-shape.

[0069] On the other hand, the positioning of the liquid crystal panel inthe first frame becomes necessary in a so-called assembling step of theliquid crystal display device in which the liquid crystal panel ismounted on the optical sheet. Here, when the liquid crystal displaydevice is completed, the liquid crystal panel is constrained by thefirst frame and the second frame which covers at least a portion of theside surface of the first frame and hence, the necessity of such apositioning of the liquid crystal panel becomes decreased. Accordingly,in the step which places the liquid crystal panel on the optical sheet,it is sufficient to guide two sides of the liquid crystal panel by twosides of the first frame extending in the L-shape.

[0070] In this embodiment, the above-mentioned first columnar member isformed into a size which can face the side surface of the liquid crystalpanel in an opposed manner and a portion (portion A) which faces theside surface of the liquid crystal panel in an opposed manner isprojected to the side surface side of liquid crystal panel more thanother portion (portion B) which is fitted into the first opening. Forexample, when the first columnar member is formed into a circularcolumnar shape, a radius of the portion A is made larger than a radiusof the portion B. Due to such a constitution, the positioning of theliquid crystal panel in the assembling step of the liquid crystaldisplay device can be performed promptly and reliably.

[0071] The shapes of the first columnar member and the second columnarmember which have been referred in the above-mentioned constitution (12)and will be referred in the constitutions (13) to (24) respectively isnot limited to a circular columnar shape. For example, the firstcolumnar member and the second columnar member may be formed in arectangular parallelepiped shape or a hook shape or may be formed in awall shape extending along the first periphery or the second periphery.

[0072] Constitution (13):

[0073] In the above-mentioned constitution (12), “a bank” having asurface which faces a side surface of the backlight is formed on one ofa first pair of sides of the main surface of the first frame which facesthe second frame in an opposed manner (first periphery) and the firstcolumnar member is formed on this bank.

[0074] Due to such a constitution, since the position (height measuredby using the bottom surface of the first frame as the reference) of thejoining portion between the first columnar member and the first frameand such a position of the optical sheet can be aligned so that thestress and the distortion which is applied to the optical sheet at thetime of fixing the optical sheet to the first frame at the firstcolumnar member can be reduced.

[0075] Although the bank which is referred here may be formed as a wallwhich surrounds the bottom surface of the first frame, the bank may beintermittently formed in conformity with openings formed in the bottomsurface to perform the heat radiation from the first frame or to makethe first frame light-weighted.

[0076] Constitution (14):

[0077] In the above-mentioned constitution (13), the periphery of theportion of the bank where the first columnar member is formed is formedsuch that the periphery is indented toward the main surface of the firstframe (the bottom surface of the above-mentioned first frame) whichfaces the second frame in an opposed manner.

[0078] Constitution (15):

[0079] In the above-mentioned constitution (12), the second opening ofthe optical sheet is formed in the projecting portion of the opticalsheet which is projected from the side thereof which faces one of asecond pair of sides of the first frame (the second periphery of theoptical sheet) toward one of a second pair of sides (the secondperiphery of the first frame).

[0080] Constitution (16):

[0081] In the above-mentioned constitution (15), on one of a second pairof sides of the main surface of the first frame which faces the secondframe in an opposed manner (second periphery), a projecting portionwhich is formed closer to the side surface of the liquid crystal panelthan the second columnar member is mounted. This projecting portion isused for positioning the liquid crystal panel with respect to the firstframe.

[0082] Constitution (17):

[0083] In the liquid crystal display device of this example, when theperiphery of the first frame (the periphery of the bottom surface of thefirst frame) is constituted by including a first pair of sides whichface each other in an opposed manner and a second pair of sides whichextend in the direction intersecting a first pair of sides and face eachother in an opposed manner, at least one first columnar member ismounted on one (first periphery) of a first pair of sides of the mainsurface of the first frame which faces the second frame in an opposedmanner, a projecting member which faces a side surface of the liquidcrystal panel is mounted on one (second periphery) of a second pair ofsides of the main surface of the first frame which faces the secondframe in an opposed manner, a fitting member which is fitted into aperiphery of the optical sheet is mounted on the other (third periphery)of a pair of the above-mentioned first sides of the main surface of thefirst frame which faces the second frame in an opposed manner.

[0084] Further, a first opening into which the first columnar member isfitted is formed in a periphery (first periphery) of the optical sheetwhich faces one of a first pair of sides of the first frame, and afitting portion into which the fitting member is fitted is formed in aperiphery (third periphery) of the optical sheet which faces the otherof a first pair of sides.

[0085] Further, a portion of the first columnar member which faces theside surface of the liquid crystal panel in an opposed manner isprojected toward the side surface of the liquid crystal panel than otherportion of the first columnar member which is fitted into the firstopening.

[0086] Assuming that the first frame has a rectangular bottom surface,the second periphery has one end thereof joined with the first peripheryand the other end thereof joined with the third periphery. Accordingly,the first periphery, the second periphery and the third periphery arearranged in a shape of the letter π. In the constitution (17), theliquid crystal panel is positioned with respect to the first frame usingthe first columnar member and the protruding member which are arrangedin an L shape, while the optical sheet is fixed to the first frame usingthe first columnar member and the fitting member which are arranged attwo opposing sides of the letter

[0087] Constitution (18):

[0088] In the constitution (17), at least one of fitting members formedin the first frame is formed of the second columnar member, while thefitting portions formed in the optical sheet are formed at least one ofsecond openings into which the second columnar members are fitted.

[0089] Constitution (19):

[0090] In the constitution (17), a bank having a surface which faces aside surface of the backlight is formed on the other (third periphery)of a pair of the first sides of the main surface of the first framewhich faces the second frame in an opposed manner, a recessed portion isformed by indenting the bank toward the main surface of the first framewhich faces the second frame in an opposed manner (bottom surface of theabove-mentioned first frame) thus forming the fitting member, and aprojecting portion which is projected toward the other of a pair of thefirst sides (third periphery of the first frame) is formed on a side ofthe optical sheet which faces the other of a pair of the first sides ofthe first frame (third periphery of the optical sheet) thus forming thefitting portion.

[0091] In the third periphery of the first frame, a projecting portionof the optical sheet (projecting along the extending direction of thesecond periphery) is fitted into a recessed portion formed in a bank ofthe first frame. Since the optical sheet is formed in a film shape or aplanar plate shape having a main surface along the first main surface ofthe liquid crystal panel, the optical sheet can be extended or shrunkwithin the main surface in conformity with the environment in which theliquid crystal display device is used.

[0092] When the optical sheet is held by the first periphery and thethird periphery of the first frame with similar holding forces, due tothe expansion of the optical sheet along the extension direction of thesecond periphery, wrinkles are generated at a portion of the mainsurface of the optical sheet which faces the liquid crystal panel sothat the characteristics of the optical system from the backlight to theliquid crystal panel is damaged.

[0093] In the mode of the constitution (19), the holding of the opticalsheet at the third periphery of the first frame is made loose comparedto the holding of the optical sheet at the first periphery of the firstframe. Accordingly, the expansion of the optical sheet along theextension direction of the second periphery of the first frame can beabsorbed by the slight displacement of the projecting portion of theoptical sheet at the recessed portion of the bank of the first frame.

[0094] Constitution (20):

[0095] In any one of the modes of the above-mentioned constitutions (12)to (15) and constitution (18), a portion of the second columnar memberwhich faces the side surface of the liquid crystal panel (portion A) isprojected toward the side surface of the liquid crystal panel than otherportion of the second columnar member which is fitted into the secondopening (portion B).

[0096] Due to such a portion A of the first columnar member and thesecond columnar member, the liquid crystal panel can be positioned withrespect to the first frame.

[0097] Constitution (21):

[0098] In the liquid crystal display device of this example, when theperiphery of the first frame (the periphery of the bottom surface of theabove-mentioned first frame) is constituted by including a first pair ofsides which face each other in an opposed manner and a second pair ofsides which extend in the direction intersecting a first pair of sidesand face each other in an opposed manner, at least one first columnarmember is mounted on one (first periphery) of a first pair of sides ofthe main surface of the first frame which faces the second frame in anopposed manner, at least one second columnar member is mounted on one(second periphery) of a second pair of sides of the main surface of thefirst frame which faces the second frame in an opposed manner.

[0099] Further, a first opening into which the first columnar member isfitted is formed in the periphery (first periphery) of the optical sheetwhich faces one of a pair of the first sides of the first frame, while asecond opening into which the second columnar member is fitted is formedin the periphery (second periphery) of the optical sheet which faces oneof a pair of the second sides of the first frame.

[0100] Both of the first columnar member and the second columnar memberare configured to have portions (portions A) which face the sidesurfaces of the liquid crystal panel in an opposed manner. In the modeof the constitution (21), as in the case of the mode of the constitution(12), the optical sheet is held by the first columnar member and thesecond columnar member which are arranged in an L-shape in the firstframe, while the positioning of the liquid crystal panel is performed bythese first columnar member and second columnar member.

[0101] Constitution (22):

[0102] In the constitution (21), driving circuits of the liquid crystalpanel are respectively mounted on peripheries thereof along the other ofthe first pair of sides (third peripheries) and the other of the secondpair of sides (fourth peripheries) of the first frame, while the drivingcircuits of the liquid crystal panel are not mounted on peripheriesthereof along one of the first pair of sides (first peripheries) and theother of the second pair of sides (second peripheries) of the firstframe.

[0103] In the constitution (22), in the same manner as the constitution(12) and the constitution (20), when the liquid crystal panel ispositioned with respect to the first frame using the portions A of thefirst columnar member and the second columnar member (portions whichface the side surfaces of the liquid crystal panel in an opposedmanner), the driving circuit parts which are arranged on the sidesurface of the liquid crystal display panel or flexible printed circuitboards which supply signals or electric power to the drive circuit partsare brought into contact with the columnar member. Accordingly, theremay be a possibility that an error occurs in the positional alignment ofthe liquid crystal panel due to the thickness of these parts.

[0104] Accordingly, it is recommended to separate a side surface whichis used for positional alignment of the liquid crystal panel and a sidesurface which is used for supplying signals or electric power (beingmounted with a printed circuit board, a connector or the like).

[0105] When the first frame has a rectangular bottom surface, in themode of the constitution (22), one end of the first periphery is joinedto one end of the second periphery, the other end of the secondperiphery is joined to one end of the third periphery, the other end ofthe third periphery is joined to one end of the fourth periphery, andthe other end of the fourth periphery is joined to other end of thefirst periphery, whereby the rectangular profile of the bottom surfaceof the first frame is constituted in the order of the first periphery,the second periphery, the third periphery and the fourth periphery.

[0106] Constitution (23):

[0107] In any one of the above-mentioned constitutions (12) to (16), theabove-mentioned constitution (18) and the above-mentioned constitutions(20) to (22), the second opening is formed into a shape extending alongone of a second pair of sides of the first frame (second periphery)compared to the first opening. For example, while the first opening isformed into a circular shape, the second opening is formed into anelliptical shape which is elongated along the second periphery(extension direction).

[0108] In any one of the above-mentioned constitutions (12) to (16), theabove-mentioned constitution (18) and the above-mentioned constitutions(20) to (22), the forming position of the second opening in the opticalsheet of the liquid crystal display device which becomes the presumptionof these constitutions is arranged away from the forming position of thefirst opening along the extension direction of the second periphery by agiven distance. Accordingly, when the optical sheet is expanded in theabove-mentioned manner, the given distance is increased.

[0109] Based on such a prerequisite, if the first opening of the opticalsheet is firmly held by the first columnar member and the second openingof the optical sheet is firmly held by the second columnar member tosame degree, the expanded optical sheet is deflected between the firstopening and the second opening so that the optical conditions betweenthe backlight and the liquid crystal panel is damaged.

[0110] To the contrary, according to one example of the presentinvention, by elongating the second opening along the second periphery,the conventional deflection of the optical sheet derived from thepositional displacement between the second columnar member and thesecond opening into which the second columnar member is inserted causedby the expansion of the optical sheet can be prevented. Accordingly, theoptical problem caused by the deflection of the optical sheet can bedissolved.

[0111] Constitution (24):

[0112] In any one of the above-mentioned constitutions 12 to 23, theperiphery of the first frame along a pair of the second sides (thesecond and fourth peripheries) are more elongated than the periphery ofthe first frame along a pair of the first sides (the first and thirdperipheries).

[0113] The present invention is not limited to the above-mentionedconstitutions and constitutions of embodiments which will be explainedlater and various modification can be made without departing from thetechnical concept of the present invention.

[0114] These and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0115]FIG. 1 is a developed perspective view of an essential part of aliquid crystal display device for schematically explaining a structurefor positioning and holding an optical sheet to a lower frame and astructure for positioning a liquid crystal panel to explain the firstembodiment of a liquid crystal display device according to the presentinvention;

[0116]FIG. 2 is a cross-sectional view of an essential part afterconstitutional members are assembled to explain the first embodiment ofthe liquid crystal display device according to the present invention;

[0117]FIG. 3 is a plan view of a lower frame used in the firstembodiment of the liquid crystal display device according to the presentinvention;

[0118]FIG. 4 is a developed perspective view for explaining the overallconstitution of the first embodiment of the liquid crystal displaydevice according to the present invention in which a light guide plate,an optical sheet and a liquid crystal panel are mounted on the lowerframe shown in FIG. 3 and these members are covered with an upper frame;

[0119]FIG. 5 is a plan view for explaining a structural example of aliquid crystal panel of the liquid crystal display device shown in FIG.4;

[0120]FIG. 6 is a plan view for explaining a first constitutionalexample of an optical sheet holding structure which loosely holds anoptical sheet formed on other side different from a side to which thepositioning function of the optical sheet in the first embodiment of theliquid crystal display device according to the present invention isgiven;

[0121]FIG. 7 is a plan view for explaining a second constitutionalexample of an optical sheet holding structure which loosely holds anoptical sheet formed on other side different from a side to which thepositioning function of the optical sheet in the first embodiment of theliquid crystal display device according to the present invention isgiven;

[0122]FIG. 8 is a plan view for explaining a third constitutionalexample of an optical sheet holding structure which loosely holds anoptical sheet formed on other side different from a side to which thepositioning function of the optical sheet in the first embodiment of theliquid crystal display device according to the present invention isgiven;

[0123]FIG. 9 is a plan view for explaining a fourth constitutionalexample of an optical sheet holding structure which loosely holds anoptical sheet formed on other side different from a side to which thepositioning function of the optical sheet in the first embodiment of theliquid crystal display device according to the present invention isgiven;

[0124]FIG. 10 is a plan view of an essential part which shows the firstconstitutional example of the optical sheet holding structure formed onthe side close to the fixing side explained in FIG. 6;

[0125]FIG. 11 is a plan view of an essential part which shows the secondconstitutional example of the optical sheet holding structure formed onthe side close to the fixing side explained in FIG. 6;

[0126]FIG. 12 is a perspective view of an essential part for explainingan example of an optical sheet holding structure at a side close to thefixing side explained in FIG. 6 or at a side which faces the fixing sideexplained in FIG. 7 in an opposed manner;

[0127]FIG. 13 is a cross-sectional view of an essential part afterconstitutional members are assembled to explain the second embodiment ofthe liquid crystal display device according to the present invention;

[0128]FIG. 14 is a cross-sectional view of an essential part afterconstitutional members are assembled to explain the third embodiment ofthe liquid crystal display device according to the present invention;

[0129]FIG. 15 is a developed perspective view for explaining an exampleof a detail of the overall constitution of the liquid crystal displaydevice according to the present invention;

[0130]FIG. 16 is an appearance view for showing one example of anotebook type personal computer on which the liquid crystal displaydevice according to the present invention is mounted;

[0131]FIG. 17A and FIG. 17B are schematic views for explaining aconventional example of positioning of an optical sheet in a liquidcrystal display device and a holding structure thereof in an enlargedform, wherein FIG. 17A is a cross-sectional view and FIG. 17B is adeveloped perspective view;

[0132]FIG. 18A and FIG. 18B are schematic views for explaining anotherconventional example of positioning of an optical sheet in a liquidcrystal display device and a holding structure thereof in an enlargedform, wherein FIG. 18A is a cross-sectional view and FIG. 18B is a planview; and

[0133]FIG. 19 is a developed perspective view of an essential part forexplaining still another conventional example of positioning of anoptical sheet in a liquid crystal display device and a holding structurethereof.

DETAILED DESCRIPTION

[0134] Embodiments of a liquid crystal display device according to thepresent invention are explained in detail in conjunction with drawingsshowing the embodiments.

[0135]FIG. 1 is a developed perspective view of an essential part of aliquid crystal display device for schematically explaining a structurefor positioning and holding an optical sheet to a lower frame and astructure for positioning a liquid crystal panel to explain the firstembodiment of a liquid crystal display device according to the presentinvention. Further, FIG. 2 is a cross-sectional view of an essentialpart after constitutional members are assembled to explain the firstembodiment of the liquid crystal display device according to the presentinvention.

[0136] In FIG. 1 and FIG. 2, reference symbol MCA indicates a lowerframe formed by resin molding (also referred to as a mold case, however,this element being explained as “lower frame” hereinafter), DH indicatesa recessed portion (indentation) for positioning and holding an opticalsheet OPS, and PIN-C indicates a columnar member for performing thepositioning by passing through a through hole HOL-C formed in aprojecting portion (also referred to as a flap or a tab) TAB which isformed in the optical sheet OPS. This columnar member PIN-C alsofunctions as a guide for positioning a liquid crystal panel PNL.

[0137] The shape of the projecting portion TAB is not limited to arectangular shape shown in the drawing and may be a shape having bothprojecting side peripheries arranged in a non-parallel form or in asemicircular form or in other form. It is preferable to make the shapeof the recessed portion formed in the lower frame MCA correspond to theshape of the projecting portion TAB.

[0138] The optical sheet OPS of this embodiment is formed of four sheetsin total consisting of two prism sheets PRS and two light diffusionsheets SPS which are laminated to upper and lower surfaces (front andback surfaces) of these prism sheets PRS. However, the optical sheet OPSis not limited to such a constitution. That is, a combination of oneprism sheet and one light diffusion sheet, a combination of two prismsheets and one light diffusion sheet, or a combination of one prismsheet and two light diffusion sheets or other various combinations canbe adopted as the optical sheet OPS.

[0139] The liquid crystal display device is assembled as follows. Firstof all, a reflection sheet RFS is mounted on the lower frame MCA and alight guide plate GLB which constitutes a backlight is fitted into thelower frame MCA such that the light guide plate GLB is positioned abovethe reflection sheet RFS. The light guide plate GLB is positioned suchthat the light guide plate GLB is seated in a frame portion for mountinglight guide plate which is formed in the lower frame MCA.

[0140] Then, the columnar member PIN-C is allowed to pass through thethrough holes HOL-C which are formed in the respective projectingportions TAB of the respective sheets which constitutes the opticalsheet OPS from the direction indicated by an arrow A in FIG. 1, and theprojecting portion TAB is seated in the recessed portion DH and is fixedby a one-sided adhesive tape ATP. By forming a hole through which thecolumnar member PIN-C passes in the one-sided adhesive tape ATP, theoptical sheet OPS can be firmly fixed.

[0141] After positioning and fixing the optical sheet OPS, the liquidcrystal panel PNL is positioned on the optical sheet OPS using aliquid-crystal-panel-side side wall of the columnar member PIN-Cindicated by a line C-C in FIG. 1 and FIG. 2 as a guide. The holding ofother sides of the optical sheet OPS and the liquid crystal panel willbe explained later.

[0142]FIG. 3 is a plan view of a lower frame used in the firstembodiment of the liquid crystal display device according to the presentinvention. The drawing shows a plan view as seen from the liquid crystalpanel side. The lower frame MCA of this embodiment has an approximatelyrectangular shape with a bank portion DAM which has a height at an upperframe side formed on the periphery thereof. A linear lamp (cold cathodefluorescent tube) which constitutes a backlight is arranged at a lowerside of FIG. 3, while a gate driver side and a drain driver side arearranged at a left side and a lower side of FIG. 3 respectively.

[0143] Respective sides of the lower frame MCA are connected to eachother by a plurality of crosspieces BRDG which are arranged taking themechanical strength and the heat radiation into account. Engagingrecessed portions ALV-R, ALV-L of the lower frame MCA which are formedin the bank portion DAM at left and right sides which intersect thelower side on which the linear lamp is arranged are provided forengagement with the light guide plate not shown in the drawing andreceive engaging projections SSTP formed on the corresponding sides ofthe light guide plate.

[0144] A liquid crystal filling and sealing opening of the liquidcrystal panel is positioned at a right side of the lower frame MCA andthe recessed portion DH which has been explained with respect to FIG. 1and FIG. 2 is formed in the bank DAM avoiding a portion where the liquidcrystal filling and sealing opening is formed. The columnar member PIN-Cis provided to the recessed portion DH.

[0145] In this embodiment, an optical sheet holding structure whichloosely holds the corresponding side of the optical sheet OPS and willbe explained later in conjunction with FIG. 9 and FIG. 10 is provided toan upper side (a neighboring periphery of the periphery which has therecessed portion DH) of the lower frame MCA. The columnar member PIN-Sis also formed in the optical sheet holding structure provided to thisupper side. The positional displacement of the optical sheet OPS withrespect to the lower frame MCA having such a rectangular bottom surfaceas shown in FIG. 3 (the rectangular bottom surface includes vacancyappearing partially at an outline thereof) is prevented by two sidesthereof (upper and right sides thereof shown in FIG. 3) extended in theL-shape from one corner thereof (an upper-right corner shown in FIG. 3).

[0146]FIG. 4 is a developed perspective view for explaining the overallconstitution of the first embodiment of the liquid crystal displaydevice according to the present invention. As shown in the drawing, alight guide plate, an optical sheet and a liquid crystal panel aremounted on the lower frame shown in FIG. 3 and these members are coveredwith an upper frame. FIG. 5 is a plan view for explaining only a liquidcrystal panel shown in FIG. 4.

[0147] As shown in FIG. 4, the light guide plate GLB, the optical sheetOPS and the liquid crystal panel PNL are assembled to the lower frameMCA, the upper frame SHD made of metal is mounted on the liquid crystalpanel PNL, and these members have peripheries thereof fixed to and areintegrally formed with the lower fame MCA thus completing the liquidcrystal display device (liquid crystal display module).

[0148] That is, by connecting projections PRJN which are formed on thelower frame MCA to fixing holes HOLLS formed in the periphery of theupper frame SHD, or by bending paws NL which are formed on the upperframe SHD over a back surface of the lower frame MCA, the upper frameSHD and the lower frame MCA are fixed to each other. In FIG. 5, a regionin the inside of a main surface of the liquid crystal panel PNL which isindicated by a chained line AR indicates an effective display region ofthe liquid crystal panel.

[0149] Engaging projections SSTP are formed on two sides of the lightguide plate GLB and are engaged with the engaging recessed portionsALV-R, ALV-L (see FIG. 3 with respect to ALV-L) formed in the lowerframe MCA so that the light guide plate GLB is housed in the lower frameMCA while being restricted to a given position.

[0150] As shown in FIG. 5, a gate driver IC and a drain driver IC arerespectively directly mounted on two neighboring peripheral sides of theliquid crystal panel PNL (referred to as “FCA system” or “COG” system)and these driver ICs are respectively connected to an interface circuitboard FPC3 through flexible printed circuit boards FPC1, FPC2. Withrespect to the flexible printed circuit FPC2, GPAD indicates a groundpad, CDC indicates an electronic part such as capacitor chip or thelike, and HOLE indicates a position restricting hole.

[0151] The flexible printed circuit board FPC2 is folded back to theback surface of the liquid crystal panel PNL as indicated by an arrow ata portion of a bent window BNTW and is connected to the interfacecircuit board FPC3 which is positioned at a back surface of the lowerframe MCA which, in turn, is positioned at a back surface of a laminatedbody made of the liquid crystal panel and the light guide body. Here,although the flexible printed circuit board FPC1 of the gate driver isalso bent in the same manner, the flexible printed circuit board FPC1 isfixed to the back surface of the lower-side substrate of the liquidcrystal panel PNL.

[0152]FIG. 6 to FIG. 9 relate to the optical sheet OPS in the firstembodiment of the liquid crystal display device according to the presentinvention. These drawing are plan views which explain variousconstitutional examples of optical sheet holding structures whichloosely hold the optical sheet OPS and are formed on the sides otherthan the side of the lower frame MCA to which the positioning functionis given (the side in which the projecting portion TAB-C having athrough hole HOL-C is formed).

[0153] The above-mentioned positioning function is given to the rightside (in the drawing) of the optical sheet OPS and the optical sheet OPSis fixed to the lower frame after using this positioning function.However, when the optical sheet OPS is fixed in the same manner at othersides, the deformation such as wrinkles or the like are generated due tothe change of an environment. Accordingly, the holding of the opticalsheet OPS at the sides other than the side to which the above-mentionedpositioning function is given (also referred to as “a fixing side” forthe convenience sake) is required to be loose.

[0154] In the constitution shown in FIG. 6, projecting portions TAB-Sare formed on the side (the upper side) adjacent to the above-mentionedfixing side and through holes HOL-S which are large enough to allow thecolumnar members PIN-S shown in FIG. 3 to loosely pass therethrough areformed on the projecting portions TAB-S. Due to such a constitution, themovement of the optical sheet OPS is not obstructed in theabove-mentioned neighboring side and hence, the deformation of theoptical sheet OPS which may be brought about by the environmental changecan be obviated.

[0155] With respect to the optical sheet OPS shown in FIG. 7, projectingportions TAB-R are formed on the side which is arranged opposite to thefixing side and the optical sheet OPS is loosely held by a holdingmechanism which will be explained later in conjunction with FIG. 12.

[0156] With respect to the optical sheet OPS shown in FIG. 8, throughholes HB which are similar to the through holes HOL-S formed in theprojecting portions TAB-S shown in FIG. 6 are formed on the sideadjacent to the fixing side and the optical sheet OPS is held byallowing columnar members similar to those shown in FIG. 6 to looselypass through these through holes HB.

[0157] In FIG. 9, through holes HB which are similar to the throughholes HB shown in FIG. 8 are formed in the side which is arrangedopposite to the fixing side of the optical sheet OPS and the opticalsheet OPS is held by allowing columnar members similar to those shown inFIG. 6 to loosely pass through these through holes HB.

[0158]FIG. 10 and FIG. 11 are plan views of the essential part of theoptical sheet OPS. These drawings show the state in which, as explainedin conjunction with FIG. 6, the projecting portion TAB-S is formed onthe side (upper side) adjacent to the fixing side and the through holeHOL-S which is large enough to allow the columnar member PIN-S shown inFIG. 3 to loosely pass therethrough is formed in the projecting portionTAB-S.

[0159] With respect to the through holes HOL-S formed in the opticalsheet OPS, in FIG. 10, the holes HOL-S is formed in an elliptical shapewhich has a long axis thereof extending in the direction parallel to theside and a columnar member PIN-S having a diameter smaller than theshort-axis diameter of the through hole HOL-S is mounted on the lowerframe MCA side.

[0160] Further, in FIG. 11, a through hole HOL-S which is formed in theoptical sheet OPS is formed in a circular shape and a columnar memberPIN-S having a diameter smaller than a diameter of the circular shape ismounted on the lower frame MCA side.

[0161] The shape of through holes HOL-S which are formed in the opticalsheet OPS in FIG. 10 and FIG. 11 and the shape of the columnar membersPIN-S which are formed on the lower frame side and pass through thethrough holes HOL-S may be shapes other than the above-mentioned shapes.For example, the through hole HOL- S may be formed in an oblong shape, apolygonal shape, a slit-shape or the like, for example, while the shapeof the columnar member PIN-S may have an elliptical cross section, anoblong cross section, a polygonal cross section, a semi-elliptical crosssection, or other shape.

[0162]FIG. 12 is a perspective view of an essential part for explaininga structural example for loosely holding an optical sheet at a sideadjacent to the fixing side explained in FIG. 6 or at a side which isarranged opposite to the fixing side explained in FIG. 7.

[0163] Although the structure in which the optical sheet is loosely heldat the side arranged opposite to the fixing side is explained as anexample here, a structure which loosely holds the optical sheet at theside adjacent to the fixing side will perform the same function.

[0164] At one portion or two or more portions on the side which isarranged opposite to the fixing side of the optical sheet OPS,projecting portions TAB-R similar to those explained in conjunction withFIG. 7 are provided. On the other hand, a pair of erecting walls TS areformed at the lower frame MCA side while forming a gap therebetweenwhich is slightly larger than the width of the projecting portion TAB-Rin the direction parallel to the side of the lower frame MCA.

[0165] The projecting portion TAB-R of the optical sheet OPS is insertedbetween a pair of erecting walls TS and a press member BKT is fitted onthe projecting portion TAB-R in the direction of an arrow so as toconstrain the projecting portion TAB-R from above. The projectingportion TAB-R is loosely held in a space defined between a pair oferecting walls TS and the press member BKT.

[0166] According to the above-mentioned embodiment, the accuratepositioning and the holding of the optical sheet OPS which can preventthe removal and the disengagement of the optical sheet OPS from thelower frame MCA are performed at one side and, at the same time, itbecomes possible to obviate the deformation of the optical sheet OPSwhich may be caused by the environmental change or the like.

[0167]FIG. 13 is a cross-sectional view of an essential part afterconstitutional members are assembled to explain the second embodiment ofthe liquid crystal display device according to the present invention. Inthis embodiment, in place of the columnar member PIN-C of the lowerframe MCA explained in conjunction with FIG. 2, a hole NT is formed inthe lower frame MCA, an insertion member BT having a pin shape with ahead is allowed to pass through a through hole HOLC formed in theoptical sheet OPS and is fitted into the hole NT under pressure so as toposition and hold the optical sheet OPS. Although this embodiment issimilar to the first embodiment as explained in conjunction with FIG. 1with respect to the holding of other sides of the optical sheet OPS andthe other constitutions, the columnar member may be replaced with aninsertion member having a pin shape with a head which is similar to theabove-mentioned insertion member BT having the pin shape with the headwhich is loosely engaged with the through hole formed in the opticalsheet.

[0168] In this embodiment, a side wall FF of the head of the insertionmember BT at the liquid crystal panel PNL side can be used as apositioning guide for the liquid crystal panel. Accordingly, even whenthere exists some difference in size with respect to the liquid crystalpanel, the insertion member BT can be made to function as a desiredpositioning guide by changing the size of the head of the insertionmember BT.

[0169] Further, in this embodiment, by adopting a method in which theinsertion member BT is prepared in the state that the insertion memberBT passes through the through hole HOL-C formed in the optical sheet OPSwhich is integrally formed by preliminarily laminating a plurality ofsheets and then the insertion member BT is pushed into the hole NT ofthe lower frame MCA, it becomes possible to obtain an advantage that theassembling operation can be simplified.

[0170] Also according to this embodiment, the accurate positioning andthe holding of the optical sheet OPS which can prevent the removal andthe disengagement of the optical sheet OPS from the lower frame MCA areperformed at one side and, at the same time, it becomes possible toobviate the deformation of the optical sheet OPS which may be caused bythe environmental change or the like.

[0171]FIG. 14 is a cross-sectional view of an essential part afterconstitutional members are assembled to explain the third embodiment ofthe liquid crystal display device according to the present invention. Inthis embodiment, a cylindrical sleeve SB similar to the cylindricalsleeve SB which is explained in conjunction with the above-mentionedFIG. 17A and FIG. 17B is fitted on the columnar member PIN-C of thelower frame MCA which is explained in conjunction with FIG. 2 thusfixing the optical sheet OPS to the columnar member PIN-C such that theoptical sheet OPS is not disengaged from the columnar member PIN-C.

[0172] The cylindrical sleeve SB can be made to function as apositioning guide of the liquid crystal panel PNL by changing thediameter of the cylindrical sleeve SB. Further, by changing the size ofthe cylindrical sleeve SB or by adjusting a bulging quantity of a wallof a side surface which faces the liquid crystal panel PNL in an opposedmanner, it becomes possible to make the cylindrical sleeve SB functionas a desired positioning guide. With respect to the holding of othersides of the optical sheet OPS and other constitutions, this embodimentis similar to the first embodiment which is explained in conjunctionwith FIG. 1 and the above-mentioned second embodiment.

[0173] Also according to this embodiment, the accurate positioning ofthe optical sheet OPS on the lower frame MCA and the holding of theoptical sheet OPS which can prevent the removal and the disengagement ofthe optical sheet OPS from the lower frame MCA are performed at one sideof the optical sheet OPS and, at the same time, it becomes possible toobviate the deformation of the optical sheet OPS which may be caused bythe environmental change or the like.

[0174] According to the embodiments which have been describedheretofore, the positioning and the holding of the optical sheet to thelower frame can be reliably performed and, at the same time, thepositioning of the liquid crystal panel which is mounted on the opticalsheet in a laminated manner can be performed in common with the aboveoperations so that the removal or the displacement of the optical sheetat the time of conveying or transporting the lower frame into which theoptical sheet is incorporated can be suppressed. Further, since theman-hours for assembling can be reduced, the assembling operation can besimplified and the manufacturing cost can be reduced.

[0175]FIG. 15 is a developed perspective view for explaining an exampleof a detail of the overall constitution of the liquid crystal displaydevice according to the present invention. Different from the liquidcrystal display panel shown in FIG. 4 and FIG. 5 which constitutes aso-called FCA or COG, in a liquid crystal panel used in this liquidcrystal display device (liquid crystal display module), driving circuits(a gate driver, a drain driver) are mounted on a tape carrier packageTCP and are connected to input terminal wiring which is pulled out tothe periphery of the liquid crystal panel

[0176] In FIG. 15, SHD indicates an upper frame made of a metal plate(also referred to as “metal frame”), WD indicates a display window, INSIto INS3 indicate insulation sheets, PCB1 to PCB3 indicate printedcircuit boards (PCB1: drain-side circuit board (video signal linedriving circuit board, PCB2: gate-side circuit board (scanning signalline driving circuit board, PCB3: interface circuit board), JN1 to JN3indicate joiners which electrically connect the circuit boards PCB1 toPCB3 to each other, TCP1 and TCP2 indicate tape carrier packages (TCP),PNL indicates a liquid crystal panel, GC indicates a rubber cushion, ILSindicates a light shielding spacer, PRS indicates a prism sheet, SPSindicates a diffusion sheet, GLB indicates a light guide plate, RFSindicates a reflection sheet, MCA indicates a lower frame (a mold frameformed by integral molding), MO indicates an opening of the lower frameMCA, LP indicates a fluorescent tube (also referred to as “a tubularlight source” or “a linear lamp”: usually a cold cathode fluorescenttube), LPC indicates a lamp cable, GB indicates a rubber bushing whichsupports the fluorescent lamp LP, BAT indicates a double-sided adhesivetape, BL indicates a backlight which is constituted of the fluorescenttube LP, the light guide plate GLB, a lamp reflection sheet LS and thelike. These components are laminated in accordance with the positionalrelationship shown in the drawing so as to assemble a liquid crystaldisplay device (a liquid crystal display module) MDL.

[0177] The liquid crystal display module MDL has two kinds ofhousing/holding members (cases) consisting of the lower frame MCA andthe upper frame SHD. The liquid crystal display module MDL is formed bymerging the metallic upper frame SHD which houses and fixes theinsulation sheets INS1 to INS3, the printed circuit boards PCB1 to PCB3and the liquid crystal panel PNL therein and the lower frame MCA whichhouses the backlight BL consisting of the fluorescent tube LP, the lightguide plate GLB, the prism sheets PRS, the light diffusion sheet SPS andthe like.

[0178] A drain driver IC (an integrated circuit chip) which is servedfor supplying video signals to respective pixels of the liquid crystalpanel PNL is mounted on the drain-side circuit board PCB1, while a gatedriver IC which is served for scanning pixels is mounted on thegate-side circuit board PCB2.

[0179] Further, on the interface circuit board PCB3, an integratedcircuit chip which receives video signals from an external host computerand receives control signals such as timing signals and the like, atiming converter TCON which generates clock signals by processing timingand the like are mounted.

[0180] The clock signals which are generated by the timing converterTCON are supplied to an integrated circuit chip mounted on the videosignal line driving circuit board PCB1 through clock signal lines CLLmounted on the interface circuit board PCB3 and the video signal linedriving circuit board PCB1.

[0181] The interface circuit board PCB3 and the video signal linedriving circuit board PCB1 are constituted of multilayered wiring boardsand the clock signal lines CLL are formed as inner-layer wiring of theinterface circuit board PCB3 and the video signal line driving circuitboard PCB1.

[0182] The drain-side circuit board PCB1 for driving TFTs, the gate-sidecircuit board PCB2 and the interface circuit board PCB3 are connected tothe liquid crystal panel PNL through the tape carrier packages TCP1,TCP2 and these circuit boards are connected to each other through thejoiners JN1 to JN3.

[0183]FIG. 16 is an appearance view for showing one example of anotebook type personal computer on which the liquid crystal displaydevice according to the present invention is mounted. Theabove-mentioned liquid crystal display device is mounted on a displaypart of this notebook type personal computer and the linear lamp LP ismounted on a lower side of the liquid crystal display device. A body ofthe notebook type personal computer includes a key board part and housesa host computer (a CPU) and other information processing equipmenttherein.

[0184] The liquid crystal display device according to the presentinvention is not limited to the notebook type personal computer shown inFIG. 7 and it is needless to say that the liquid crystal display deviceis applicable to a display monitor, a television receiver set and adisplay device of other equipment in the same manner.

[0185] Further, the application of the present invention is not limitedto the liquid crystal display device using the above-mentioned activematrix type liquid crystal panel. That is, the present invention is alsoapplicable to a display device which adopts a simple matrix type liquidcrystal panel or various other kinds of panel-type display devices inthe same manner.

[0186] As has been described heretofore, the present invention canprovide the liquid crystal display device which has a structure capableof suppressing the removal or disengagement of the optical sheetassembled to the lower frame at the time of transporting or at the timeof transferring so as to reduce man-hours for assembling and simplifyingthe operation and reducing the manufacturing cost by ensuring thereliable positioning and holding of the optical sheet to the lower frameand by using the positioning guide of a liquid crystal panel andpositioning means of the optical sheet in common.

[0187] While we have shown and described several embodiments inaccordance with the present invention, it is understood that the same isnot limited thereto but is susceptible of numerous changes andmodifications as known to those skilled in the art, and we therefore donot wish to be limited to the details shown and described herein butintend to cover all such changes and modifications as are encompassed bythe scope of the appended claims.

What is claimed is:
 1. A liquid crystal display device comprising aliquid crystal panel, a backlight which includes an optical sheet facingone main surface of the liquid crystal panel in an opposed manner, amold case which houses the backlight therein, and a metal frame whichforms a picture frame for exposing an effective display area of theother main surface of the liquid crystal panel and has side walls whichare engaged with side walls of the mold case, wherein a columnar memberwhich settles the liquid crystal panel at a given position is formed ona periphery of the mold case, and an opening is formed at a side portionof the optical sheet which corresponds to the periphery of the moldcase, and the optical sheet is held on the mold frame by allowing thecolumnar member to pass through the opening.
 2. A liquid crystal displaydevice according to claim 1, wherein the optical sheet includes at leastone light diffusion sheet or at least one prism sheet, and the openingof the optical sheet is formed in a projecting portion which is formedon the periphery of the optical sheet.
 3. A liquid crystal displaydevice according to claim 2, wherein a recessed portion is formed in theperipheral portion of the mold case and, the columnar member is mountedon the recessed portion, and the projecting portion of the optical sheetis accommodated in the recessed portion.
 4. A liquid crystal displaydevice according to claim 1, wherein the columnar member of the moldcase is allowed to pass through the opening formed in the optical sheetand the optical sheet is fixed to the periphery of the mold case wherethe columnar member is mounted using an adhesive tape.
 5. A liquidcrystal display device according to claim 1, wherein an optical sheetholding structure which loosely holds the optical sheet compared to thecolumnar member is provided to at least one of other peripheries of themold case which are arranged close to or opposite to the periphery ofthe mold case on which the columnar member is mounted.
 6. A liquidcrystal display device according to claim 5, wherein the optical sheetholding structure includes other columnar member which is formed on oneof the other peripheries of the mold case and other opening which isformed in the periphery of the optical sheet along at least one of otherperipheries of the mold case, and the other columnar member is arrangedto loosely pass through the other opening compared to the passingthrough of the columnar member to the opening.
 7. A liquid crystaldisplay device according to claim 5, wherein the optical sheet holdingstructure includes other recessed portion which is formed in one of theother peripheries of the mold case and other projecting portion which isformed on the periphery of the optical sheet to be seated in the otherrecessed portion.
 8. A liquid crystal display device according to claim7, wherein the optical sheet holding structure is provided with adisengagement restriction member which restricts the disengagement ofthe other projecting portion of the optical sheet from the otherrecessed portion of the mold case.
 9. A liquid crystal display deviceaccording to claim 1, wherein the columnar member is integrally formedwith the mold case.
 10. A liquid crystal display device according toclaim 1, wherein the columnar member is formed separately from the moldcase and is fitted into a hole formed in the mold case.
 11. A liquidcrystal display device according to claim 1, wherein the size of thecolumnar member differs between a portion thereof for holding theoptical sheet and other portion thereof in the direction opposite to oneof the main surfaces of the liquid crystal panel.
 12. A liquid crystaldisplay device comprising a liquid crystal panel, a backlight which isarranged to face a first main surface of the liquid crystal panel in anopposed manner, an optical sheet which is arranged between the firstmain surface of the liquid crystal panel and the backlight, a firstframe which accommodates the backlight, and a second frame which isformed in a picture frame and covers a periphery of a second mainsurface of the liquid crystal panel which faces the first main surfaceand at least a portion of a side surface of the mold case, wherein theperiphery of the first frame includes a first pair of sides which faceeach other in an opposed manner and a second pair of sides which extendin the direction intersecting a first pair of sides and face each otherin an opposed manner, at least one first columnar member is mounted onone of a first pair of sides of the main surface of the first framewhich faces the second frame in an opposed manner, at least one secondcolumnar member is mounted on one of a second pair of sides of the mainsurface of the first frame which faces the second frame in an opposedmanner, a first opening into which the first columnar member is fittedis formed in a periphery of the optical sheet which faces one of a firstpair of sides of the first frame and a second opening into which thesecond columnar member is fitted is formed in a periphery of the opticalsheet which faces one of a second pair of sides, and a portion of thefirst columnar member which faces a side surface of the liquid crystalpanel in an opposed manner is projected toward a side surface of theliquid crystal panel than other portion which is fitted into the firstopening of the first columnar member.
 13. A liquid crystal displaydevice according to claim 12, wherein a bank having a surface whichfaces a side surface of the backlight is formed on one of a first pairof sides of the main surface of the first frame which faces the secondframe in an opposed manner and the first columnar member is formed onthis bank.
 14. A liquid crystal display device according to claim 13,wherein the periphery of the portion of the bank where the firstcolumnar member is formed is formed such that the periphery is indentedtoward the main surface of the first frame which faces the second frame.15. A liquid crystal display device according to claim 12, wherein thesecond opening of the optical sheet is formed in the projecting portionof the optical sheet which is projected from the side of the opticalsheet which faces one of a second pair of sides of the first frametoward one of a second pair of sides.
 16. A liquid crystal displaydevice according to claim 15, wherein on one of a second pair of sidesof the main surface of the first frame which faces the second frame inan opposed manner, a projecting portion which is formed closer to theside surface of the liquid crystal panel than the second columnar memberis mounted.
 17. A liquid crystal display device comprising a liquidcrystal panel, a backlight which is arranged to face a first mainsurface of the liquid crystal panel in an opposed manner, an opticalsheet which is arranged between the first main surface of the liquidcrystal panel and the backlight, a first frame which accommodates thebacklight, and a second frame which is formed in a picture frame andcovers a periphery of a second main surface of the liquid crystal panelwhich faces the first main surface and at least a portion of a sidesurface of the first frame, wherein the periphery of the first frameincludes a first pair of sides which face each other in an opposedmanner and a second pair of sides which extend in the directionintersecting a first pair of sides and face each other in an opposedmanner, at least one first columnar member is mounted on one of a firstpair of sides of the main surface of the first frame which faces thesecond frame, a projecting member which faces a side surface of theliquid crystal panel is mounted on one of a second pair of sides of themain surface of the first frame which faces the second frame in anopposed manner, a fitting member which is fitted into a periphery of theoptical sheet is mounted on the other of a pair of the first sides ofthe main surface of the first frame which faces the second frame in anopposed manner, a first opening into which the first columnar member isfitted is formed in a periphery of the optical sheet which faces one ofa first pair of sides of the first frame and a fitting portion intowhich the fitting member is fitted is formed in a periphery of theoptical sheet which faces the other of a first pair of sides, and aportion of the first columnar member which faces a side surface of theliquid crystal panel is more projected toward the side surface of theliquid crystal panel than other portion of the first columnar memberwhich is fitted into the first opening.
 18. A liquid crystal displaydevice according to claim 17, wherein at least one of fitting membersformed in the first frame is formed of the second columnar member andthe fitting portions formed in the optical sheet are formed at least oneof second openings into which the second columnar members are fittedinto.
 19. A liquid crystal display device according to claim 17, whereina bank having a surface which faces a side surface of the backlight isformed on the other of a pair of the first sides of the main surface ofthe first frame which faces the second frame in an opposed manner, thefitting member formed in the first frame is formed as a recessed portionby indenting the bank toward the main surface of the first frame whichfaces the second frame in an opposed manner, and the fitting portionformed in the optical sheet is formed as a projecting portion which isprojected from a side of the optical sheet which faces the other of apair of the first sides of the first frame to the other of a pair of thefirst sides of the first frame.
 20. A liquid crystal display deviceaccording to claim 12, wherein a portion of the second columnar memberwhich faces the side surface of the liquid crystal panel is projectedtoward the side of the liquid crystal panel than other portion of thesecond columnar member which is fitted into the second opening.
 21. Aliquid crystal display device comprising a liquid crystal panel, abacklight which is arranged to face a first main surface of the liquidcrystal panel in an opposed manner, an optical sheet which is arrangedbetween the first main surface of the liquid crystal panel and thebacklight, a first frame which accommodates the backlight, and a secondframe which is formed in a picture frame and covers a periphery of asecond main surface of the liquid crystal panel which faces the firstmain surface and at least a portion of a side surface of the firstframe, wherein the periphery of the first frame includes a first pair ofsides which face each other in an opposed manner and a second pair ofsides which extend in the direction intersecting a first pair of sidesand face each other in an opposed manner, at least one first columnarmember is mounted on one of a first pair of sides of the main surface ofthe first frame which faces the second frame in an opposed manner, atleast one second columnar member is mounted on one of a second pair ofsides of the main surface of the first frame which faces the secondframe in an opposed manner, a first opening into which the firstcolumnar member is fitted is formed in a periphery of the optical sheetwhich faces one of a first pair of sides of the first frame and a secondopening into which the second columnar member is fitted is formed in aperiphery of the optical sheet which faces one of a second pair of sidesof the first frame, and the first columnar member and the secondcolumnar member include portions which face the side surface of theliquid crystal panel in an opposed manner.
 22. A liquid crystal displaydevice according to claim 21, wherein driving circuits of the liquidcrystal panel are respectively mounted on peripheries along the other ofthe first pair of sides and the other of the second pair of sides of thefirst frame of the liquid crystal panel, and the driving circuits of theliquid crystal panel are not mounted on peripheries along one of thefirst pair of sides and one of the second pair of sides of the firstframe of the liquid crystal panel.
 23. A liquid crystal display deviceaccording to claim 12, wherein the second opening is formed into a shapeextending along one of a second pair of sides of the first framecompared to the first opening.
 24. A liquid crystal display deviceaccording to claim 12, wherein the periphery of the first frame along apair of the second sides is more elongated than the periphery of thefirst frame along a pair of the first sides.